fix layer delete

engine/canvas.cpp

@@ -441,6 +441,16 @@ void ui::Canvas::layer_add(std::string name)
     m_layers.emplace_back();
     m_layers.back().create(m_width, m_height, name);
     m_order.push_back(idx);
+    m_current_layer_idx = idx;
+}
+void ui::Canvas::layer_remove(int idx)
+{
+    for (auto& i : m_order)
+        if (i > m_order[idx])
+            i--;
+    m_layers.erase(m_layers.begin() + idx);
+    m_order.erase(m_order.begin() + idx);
+    m_current_layer_idx = std::max<int>(m_layers.size() - 1, idx);
 }
 void ui::Canvas::layer_order(int idx, int pos)
 {